Re: AFR tuning
I have both AFR meters and EGT bungs in the headers of my 284 cubic inch Merc. Also, I've done a LOT of dyno tuning of various race/performance engines. Don't spend any time worrying about idle AFR readings - if your initial advance is correct and you've set the idle screws to optimize the idle, then you're fine. Also, there is nothing really very "tuneable" in the idle circuit . . . your jets and power valves have nothing to do with it.
Where an AFR meter is more valuable is in taking the car on the road and seeing what the AFRs are at part throttle, mid-throttle and full-throttle . . . as well as when you hit the accelerator hard. You'll probably find that when jetted correctly, that you'll be on a richer side than the "perfect" 14.7 number - especially in a performance engine. While I'd love to care about only mileage, I tend to care more about performance and detonation. I like to see my AFRs under heavy throttle to be in the 13 - 13.5 area . . . as this gives me some safety in the various conditions I'm sure to see.
In my last set of runs, I was actually a bit richer than this under full throttle (around 12 to 1), but the engine ran really well, the plugs looked good, and I'm not really worried about mileage. It is important to consider what are your goals?
I wanted a conservative tune with plenty of safety margin for various environmental conditions - so being around 13 was just fine for me.
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